High shrinkage threads,yarn and fibers from acrylonitrile polymers

ABSTRACT

THIS INVENTION RELATES TO HIGH SHRINKAGE THREADS, YARN AND FIBERS FROM ACRYLONITRILE POLYMERS OF COPOLYMERS CONTAINING AT LEAST 50% BY WEIGHT OF POLYMERIZED ACRYLONITRILE AND MIXTURES THEREOF, WHEREIN THE THREAD OR YARN PRODUCED BY THE DRY SPINNING PROCESS IS EXPOSED TO ELEVATED TEMPERATURES IN THE PRESENCE OF STEAM AND IS THEN STRETCHED AND DRIED. THE SPUN THREAD OR YARN OBTAINED BY THE DRY SPINNING PROCESS MAY BE BE CONTACTED WITH SATURATED STEAM UNDER PRESSURE

United States Patent Int. Cl. C08f 3/7 6', 15/02, 15/22 US. Cl. 260-855 R 7 Claims ABSTRACT OF THE DISCLOSURE This invention relates to high shrinkage threads, yarn and fibers from acrylonitrile polymers or copolymers containing at least 50% by Weight of polymerized acrylonitrile and mixtures thereof, wherein the thread or yarn produced by the dry spinning process is exposed to elevated temperatures in the presence of steam and is then stretched and dried. The spun thread or yarn obtained by the dry spinning process may be contacted with saturated steam under pressure.

DISCLOSURE This application is a division of US. Application Ser. No. 131,490, filed Apr. 5, 1971, now U.S. Pat. 3,739,054, which in turn was a continuation of US. Application Ser. No. 755,797, filed Aug. 28, 1968, and now abandoned.

The invention relates to a process for the production of high shrinkage threads, yarn and fibres from acrylonitrile polymers or copolymers and mixtures thereof by heat treatment of the polymeric material produced which has been dry spun.

Shrinkable fibres are of special interest for the production of high bulk yarn and pile fabric having different pile thicknesses. In this process shrunk fibres are usually worked up in admixture with a certain proportion of shrinkable fibres and the spun yarn or pile fabric is contacted with hot water at about 100 C. The shrinkable fibre portion is shrunk in this treatment, so the result that the pre-shrunk fibres of a yarn form undulations and curves, a high bulk yarn is produced. When pile fabric is subjected to the same hot water treatment on the other hand, a finished product having different pile thicknesses is obtained.

The bulkiness of a yarn and the differences in pile thickness of pile fabric can therefore largely be adjusted by the amount of shrinkage the shrinkable fibres used undergo.

It is also known that shrinkable fibres of sufficient strength and elongation can be produced from certain acrylonitrile copolymers by subjecting the spinning bands obtained by the dry spinning process to relatively slight stretching, for example to 180 to 250% of the initial length, and cutting the thread bundle up into staple fibres. The maximum shrinkage which these fibres undergo on boiling is 35 to 38%. By working up these fibres alone, yarn which has a maximum boiling shrinkage of 38 to 41% can be obtained as a result of spinning the yarn right to the end. The shrinkage values obtainable on boiling fibres and yarns in this way are, however, still insufficient for some purposes.

A process for the production of high shrinkage threads, yarns and fibres from acrylonitrile polymers or copolymers containing at least 50% by weight, and preferably at least 85% by weight, of polymerized acrylonitrile,

together with other monomers compatible therewith have now been found which is characterised in that thread or yarn obtained by the dry spinning process is exposed to temperatures of 100 to 180 C. in the presence of steam and is then stretched at temperatures below 100 C. and dried.

The acrylonitrile polymers and copolymers containing at least 50% by weight, and preferably at least by weight, of polymerised acrylonitrile which can be used in the production of the spun threads are already known in the art of synthetic thread and fibre production. Polymers of this type are obtained by copolymerisation of acrylonitrile with one or more copolymerisable monoolefinically unsaturated monomers. Suitable monolefinically unsaturated monomers are, for example, methacrylonitrile, vinyl chloride, vinylidene chloride, vinyl bromide, styrene, a-methylstyrene or the esters of unsaturated carboxylic acids such as acrylic acid esters and methacrylic acid esters. Vinyl esters such as vinyl acetate, the amides of monoolefinically unsaturated carboxylic acids, such as acrylic acid amide and methacrylic acid amide, monoolefinically unsaturated carboxylic acids themselves such as acrylic acid and methacrylic acid, and other monoolefinically unsaturated compounds which contain acidic or basic groups, such as vinyl sulphonic acid, styrene sulphonic acid, m-metihacryloylaminodiphenyldisulphimide, methacrylic acid N,N-dimethylhydrazide or vinyl pyridines may also be used. The choice of comonomers is not critical in the practice of the process according to the invention. Any monoolefinically unsaturatedcompound which can be copolymerised with acrylonitrile may be used.

It is unimportant in the production of the threads and yarn by the dry spinning process whether the polymers are produced by the process of precipitation polymerisation and are then dissolved in a suitable organic solvent for spinning, or whether polymerisation of the monomer mixture is carried out in such a solvent itself. Inorganic and/or organic pigments such as titanium dioxide or colour pigments or soluble additives may be incorporated in the acrylonitrile threads when spinning them with out affecting the efficiency of the process of the invention.

When carrying out the discontinuous process according to the invention, the thread or yarn containing at least 15% by weight and preferably more than 40% by weight of water (based on the dry thread) are introduced in a freely shrinkable state into a chamber heated to to 180 C., preferably to to C. An atmosphere of steam is produced by evaporation of the water, which atmosphere in conjunction with the ambient temperature causes shrinkage of the spinning material. After termination of the shrinkage process, the thread or yarn is cooled and subjected, at a temperature below 100 C., to the after-treatment process which is described in greater detail below.

The shrinking of the individual threads only takes a few seconds, depending on the selected temperature. In order to carry out the shrinkage step, however, the period of resistance of the spinning material in the shrinkage chamber may vary from a few seconds to several minutes, depending on the amount of water in the spun material and the temperature in the chamber. A longer residence period for the shrunk material at elevated temperatures should, however, be avoided because other- Wise the colour of the unbleached and undyed threads is adversely affected.

When carrying out the process discontinuously and in particular when treating larger quantities of spun material containing little or no water, saturated steam under an absolute pressure of at least 1.1 kg. wt./cm. and preferably 1.5 to 4.0 kg. wt./cm. may be used in a pressure chamber to adjust the steam atmosphere and temperature. The spun thread or yarn is deposited for this purpose free of tension, under conditions in which it is free to shrink, in perforated metal containers which are inserted in the pressure chamber. The saturated steam is then introduced at the desired pressure into the pressure chamber which may if desired previously have been evacuated. After termination of the shrinking step, the chamber is briefly opened to relieve pressure and may be evacuated, when partial drying and cooling of the shrunk spun material occurs. The shrinking step may be completed by briefly repeating the saturated steam treatment in the pressure chamber followed by relief of pressure several times.

When carrying out the process according to the invention continuously, apparatus heated to 100 to 180 C., preferably 110 to 160 C. is preferably used. The apparatus may contain, as transport elements, drum sieves or rollers having different speeds of rotation or belts, which ensure free shrinkage of the transported spun threads or yarn when the process is carried out continuously. The water content of the spun material introduced should again be at least 15% by weight and preferably more than 40% by weight, based on the weight of thread. Spinning material containing little or no water may, of course, also be worked up in the present invention. In such a case, care should be taken to ensure the steam atmosphere, which is absolutely essential during the shrinking step, is maintained by introducing steam into the heated apparatus. There are thus two possible methods of steam treating material obtained by the dry spinning process within the given temperature range according to the invention:

(1) Dry heat treatment of wet spun material. (2) Hot steam treatment of dry or only moist spun material.

Shrinking of the spun thread or yarn can also be carried out by a combination of the discontinuous and the continuous mode of operation.

When producing the high shrinkage thread, yarn and fibre, the spun material which has been shrunk as described above is then stretched to 180 to 320% of its initial length in a water bath at temperatures below 100 C., preferably at 65 to 95 C., after having been dressed with an antistatic preparation, and is dried in a heated apparatus. The drying temperature should be of the same order as the stretching temperature in all the operations following the stretching process. In order to produce fibres, the yarn is crimped and cut up to the desired staple length.

Thread, yarn and fibre produced in this way have, on average, to 25% higher boiling shrinkage than when the spun material has been treated under known conditions and/or when after treatment is carried out above 100 C. Fibres which have a boiling shrinkage of about 50% can therefore be easily produced.

The boiling shrinkage K is determined by treating an individual thread or thin yarn of initial length (in practice measured under a pro-tension of 0.01 to 0.02 g./den.) for 5 minutes without tension with hot water at 98 to 100 C., and then chilling in a water bath of about 20 C. The length 1 is then determined under the same pre-tension after 30 minutes on the shrunk thread or yarn. which has been stored free of tension. The boiling shrinkage K is then calculated as a percentage according to the equation:

K percent) a 100 age fibres are also of special interest in the production of high bulk yarns. The following Examples illustrate more particularly the invention.

EXAMPLE 1 A copolymer of 94% by weight of acrylonitrilc, 5.5% by weight of methyl acrylate and 0.5% by weight of m methacryloylamino diphenyldisulphimide of K-value 84.5 1 is spun by the dry spinning process from a 26.5% by weight dimethylformamide solution at a draw-off speed of 338/m./min. to form a yarn of 14,000 individual threads of titre 8.5 den. This yarn which contains 16.4% of dimethylformamide is placed, free of tension, in 5 kg. portions in a perforated metal container which is then placed in a pressure chamber. The pressure chamber around which hot water circulates is evacuated. Immediately thereafter, saturated steam is introduced into the pressure chamber for 3 minutes, so that the temperatures indicated in Table I are achieved. The spun yarn which shrinks in this step is partly dried by the subsequent evacuation of the pressure chamber, and is cooled below C.

The steam treated spun yarn is then stretched continuously at 75 C. to 220% of its initial length in a Water bath which is 5 m. in length, and the yarn is then Washed with water at 50 C., dressed with an antistatic dressing and dried in a drying drum at 65 to 70 C. To produce the fibres, the stretched yarn is subjected to compression crimping and cut up into fibres mm. in length.

Details of the absolute steam pressure employed, the temperature, shinkage of the spun yarn, boiling shrinkage of the fibres according to the invention and their moisture content are shown in Table I.

The boiling shrinkage of a fibre of a spun material which has not been shrunk, but which has been aftertreated in the same manner is indicated under Example 1f which is a comparative Example.

TABLE I Experiment numbeL..- 1a 1b 1c Id 1s 1f 1 Absolute pressure oi the steam in the pressure chamber (kg. wtJcmfi) 1. 5 l. 9 2. 3 2. 5 3. 0 Temperature in the ressure chamber 110 118 124 129 133 Shrinkage oi the spun yarn in the pressure chamber (percent) 10. 7 12. 7 13. 8 14. 0 14. 2 Boiling shrinkage of the fibre (percent). 48. 0 48. 3 50. 5 51. 0 52. 0 35. 0 Moisture content of the shrunk fibre (percent) 8. 4 7. 7 8.3 8. l 7. t 8. 6

I Comparison.

EXAMPLE 2 The spun yarn described in Example 1, comprising 14,000 individual threads of titre 8.5 den., is passed con tinuously through a water bath at a temperature of 50 C. and is squeezed off between a pair of rollers so that the water content, based on the polymer, is 60 to 65%. The spun yarn is then conveyed free of tension on an endless band through a heating cupboard at 135 to C. The spun yarn shrinks by 10% in the process.

The shrunk yarn is then stretched to 220% of its initial length in water at 75 C., and is then washed with water at 50 C., dressed with an antistatic dressing and dried at 65 to 70 C. The endless yarn is crimped in a compression crimpage chamber at 50 C. and cut up into fibres of staple length 120 mm.

In a comparative test, a spun yarn which has not been shrunk is after-treated in the same manner.

In order to test the suitability of the fibres for use in high bulk yarn, a yarn of Nm 24/1 and T/m 3202 is completely spun and the shrinkage of the yarn on boiling is Determined according to Fikentscher, Cellulosecllemie, 13, 5S, (1932).

determined. When all the yarn is spun, the shrinkage of the yarn on boiling is always slightly higher than the shrinkage on boiling of the fibre put into the process.

EXAMPLE 3 A 22.5% by weight solution in dimethylformamide of a 100% acrylonitrile polymer (K-value 89) containing 0.5% titanium dioxide (based on the polymer) is spun by the dry spinning process, at a draw-off rate of 300 m./ min. to form a yarn containing 3600 individual threads of titre 11.6 den. The yarn is carried continuously through a water bath at 45 C. and is squeezed by means of rollers to a moisture content of 50 to 55%, based on the polymer. The yarn is then passed through a heating cupboard at 140 to 145 C. under conditions of free shrinkage for 3 minutes. The yarn shrinks by 12% in this step.

The shrunk yarn is stretched in a water bath at different temperatures and different stretching ratios, is dressed with an antistatic dressing, and is dried at 65 to 70 C. The temperature of the stretching vat, the stretching ratio and the shrinkage of the yarn on boiling are entered in Table III.

In a comparative test, an untreated yarn is heat treated at 85 C. under the same conditions of stretching and drying.

A solution of a copolymer of 63% by weight of acrylonitrile, 35% by weight of vinylidene chloride and 2% of m-methacryloylamino-diphenyldisulphimide in dimethylformamide (solids content of the solution 35 by weight) is spun by the dry spinning process at a draw-oft rate of 360 m./min. to form a yarn containing 5600 individual thread of titre 8.5 den. Portions of 5 kg. of this spun yarn which contains 14.8% by weight of dimethylformamide are deposited free of tension in a perforated metal container. The spun material in the metal containers is twice contacted with saturated steam at a pressure of 2 kg.wt./ cm. absolute for 3 minutes at an interval of 5 minutes, in a pressure chamber. The spun yarn which shrinks by 5.7% is dried by subsequent evacuation of the pressure chamber and is cooled below 100 C.

Samples of the steam treated yarn are continuously stretched to 190 and 220%, respectively, of their initial length, at 75 C. in a water bath, and are subsequently 6 washed with water at 50 C., dressed with an antistatic dressing, and dried at 65 to C.

Stretching, shrinking on boiling of the threads produced according to the invention, and their moisture content are summarised in Table IV. Results of comparative experiments carried out with conventionally produced shrinkage threads are also given.

TABLE IV Spun thread bundle shrunk conventionally and after-treated after-treated according to the spun thread bundle invention (comparison) Absolute pressure of the steam in the pressure chamber 2 kg. wt./cm. Stretching to of the initial length 190 220 190 220 Shrinkage of the threads on boiling 48. 8 52. 5 37. 5 39. 4 Moisture content of the threads,

percent 8. 3 6. 2 9. 3 10. 4

We claim:

'1. A high shrinkage fiber from acrylonitrile polymers, copolymers of acrylonitrile and one or more copolymerizable monoolefinically unsaturated monomers, or mixtures thereof having a boiling water shrinkage K, measured as disclosed in the specification, of at least 42.5%; said fiber prepared by the process of (1) dry-spinning said polymer, copolymer or mixture thereof;

(2) heating the fiber obtained by dry spinning said poly? mer, copolymer of mixture thereof, to a temperature of 100 C. to 180 C. in the presence of saturated steam at a pressure of 1.5 to 4.0 kg. wt./cm. with the fiber in a freely shrinkable state; then (3) stretching the fiber 180% to 320% of its initial length at a temperature below 100 C.; and then (4) drying the stretched fiber at a temperature below 2. The fiber of claim 1 having a boiling water shrinkage K, measured as disclosed in the specification of at least 50%.

3. The fiber of claim 1 wherein said heating step (2) is conducted at a temperature of C. to C.

4. The fiber of claim 1 wherein said stretching step (3) is conducted at a temperature of 65 C. to 95 C.

5. The fiber of claim 1 wherein said stretching step (3) is conducted in water.

6. The fiber of claim 1 wherein a shrinkage of at least 5.7% is effected in said fiber during the step (2) of steam treatment.

7. The fiber of claim 1 wherein the stretching in step (3) is conducted from 220% to 320% of the initial length of the fiber.

References Cited UNITED STATES PATENTS 3,164,650 1/1965 Kocay et al. 264-206 3,397,426 8/1968 Fujita et al. 264210 3,720,745 3/1973 Konig et al. 260-855 R HARRY WONG, J 11., Primary Examiner US. Cl. X.R.

260-32.6 N, 41 B, 79.3 M, 88.7 B; 264-206 

